Represents a straight tube-shaped [PrimitiveMesh] with variable width. [TubeTrailMesh] represents a straight tube-shaped mesh with variable width. The tube is composed of a number of cylindrical sections, each with the same [member section_length] and number of [member section_rings]. A [member curve] is sampled along the total length of the tube, meaning that the curve determines the radius of the tube along its length. This primitive mesh is usually used for particle trails. $DOCS_URL/tutorials/3d/particles/trails.html $DOCS_URL/tutorials/3d/particles/index.html If [code]true[/code], generates a cap at the bottom of the tube. This can be set to [code]false[/code] to speed up generation and rendering when the cap is never seen by the camera. If [code]true[/code], generates a cap at the top of the tube. This can be set to [code]false[/code] to speed up generation and rendering when the cap is never seen by the camera. Determines the radius of the tube along its length. The radius of a particular section ring is obtained by multiplying the baseline [member radius] by the value of this curve at the given distance. For values smaller than [code]0[/code], the faces will be inverted. The number of sides on the tube. For example, a value of [code]5[/code] means the tube will be pentagonal. Higher values result in a more detailed tube at the cost of performance. The baseline radius of the tube. The radius of a particular section ring is obtained by multiplying this radius by the value of the [member curve] at the given distance. The length of a section of the tube. The number of rings in a section. The [member curve] is sampled on each ring to determine its radius. Higher values result in a more detailed tube at the cost of performance. The total number of sections on the tube.